The present invention relates, in general, to a crane with a luffing jib.
German Pat. No. DE 198 24 672 A1 describes a crane having a luffing jib which includes a main boom and a plurality of individual jib members configured to telescope in and out after a disengagement of locking bolted connections results in a release of the jib members to permit their in-and-out movement through coupling with a single-stage hydraulic piston and cylinder unit. In the extended or retracted position, the jib members can be locked, whereby the cylinder housing of the piston and cylinder unit is secured at its rearward end to an inner end of the main boom. The piston rod is connected at the forward end to a guide and traction device which is positioned in parallel relation to the piston and cylinder unit and has an inner end secured to a coupling and locking unit which can be coupled and locked with receptacles of the luffing jib members. The coupling and locking unit has two coupling bolts which are actuated mechanically via a slider formed with grooves. The coupling bolts are positioned in a horizontal plane and, to the right and left, can be pushed in and withdrawn from receptacles arranged at the inner end of the respective jib member. Actuation of the slider is implemented by an axial piston and cylinder unit which is connected to the coupling and locking unit, whereby the spring-loaded locking bolt can be retracted only when the coupling and locking unit is coupled with the receptacles of the jib member being extended or retracted, and release of the coupling bolt with the respective jib member can only be effected when the respective spring-loaded locking bolt is engaged.
European Pat. No. EP 0 661 234 A1 describes a crane with a luffing jib whose individual telescopic jib members can be extended and retracted after disengagement of locking bolts connections using only a single-stage piston and cylinder unit. The jib members are bolted in the respective extended or retracted positions by locking bolts which are spring-loaded toward their locked positions. The piston rod of the single-stage piston and cylinder unit is articulated to a joint member forming the inner end of the outer jib member. An entraining device can be coupled with receptacles of the telescopic jib members and is arranged in a part of the end of the cylinder, from which the piston rod projects out. The entraining device includes a hydraulic block with confronting cylinders for the extendible and retractable bolts formed by the pistons of the cylinders and locking the respective jib member, and a hydraulic piston and cylinder unit which is arranged perpendicular to the hydraulic block for actuation of the respective locking bolt. The hydraulic elements of the engagement device so interact that the radial piston and cylinder unit can be actuated for retraction of the respective locking bolt only when the engagement device is coupled with the jib member to be extended or retracted via the locking bolt.
German Pat. No. DE 196 41 191 A1 describes a luffing jib, in particular for stationary and mobile cranes, including telescopic jib members which move in and out by means of two continuous cables, which have each an entrance side and an exit side, in conjunction with a cable drive and cable deflecting rollers. In the retracted and extended positions, the jib members are secured against relative movement in axial direction by operatively connecting each jib member to a locking device. The cable drive and two cable deflecting rollers are arranged at the base of the main boom, and a third cable deflecting roller is arranged at a cable-drive-distal end of a guide tube which is supported within each jib member via a collar and rigidly secured to the main boom. The points of attachment of the cable end are received in a holding device which is equipped with a gripper unit and slides along the guide tube.